洛谷P2845

蓝题搜索，模拟上的细节稍微有点麻烦

#include<iostream>
#include<utility>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;
#define fi(i,a,b) for(int i = a; i <= b; ++i)
#define fr(i,a,b) for(int i = a; i >= b; --i)
#define x first
#define y second
#define sz(x) ((int)(x).size())
#define pb push_back
using pii = pair<int,int>;
//#define DEBUG
const int N = 1e4+5;
int n,m;
vector<int> vec[N];
queue<int> que;
int light[N];//表示灯的状态
int connect[N];//表示是否可以连结
int vis[N];//记录是否访问过
int ans;
void bfs(int x){
    light[x] = 1;
    connect[x] = 1;
    ans++;
    que.push(x);
    while(!que.empty()){
        int temp = que.front();
        vis[temp] = 1;
        que.pop();
        if(temp % n != 0 && !connect[temp+1] && light[temp+1]) {
            connect[temp+1] = 1;
            que.push(temp+1);
        }
        if(temp % n != 1 && !connect[temp-1] && light[temp-1]){
            connect[temp-1] = 1;
            que.push(temp-1);
        }
        if(temp + n <= n * n && !connect[temp + n] && light[temp+n]){
            connect[temp+n] = 1;
            que.push(temp + n);
        }
        if(temp - n >= 1 && !connect[temp-n] && light[temp-n]){
            connect[temp - n] = 1;
            que.push(temp-n);
        }
        fi(i,0,sz(vec[temp])-1){
            int p = vec[temp][i];
            if(!light[p]){
                light[p] = 1;
                ans++;
                if(!vis[p] && ((p % n != 0 && connect[p+1])||
                    (p % n != 1 && connect[p-1])||
                    (p+n <= n*n && connect[p+n]) || (p-n>=1 && connect[p-n]))){
                    connect[p] = 1;
                    que.push(p);
                    // cout << temp << " " << p << endl;
                }

            }
        }
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    while(m--){
        int a,b,c,d;
        cin >> a >> b >> c >> d;
        int x = (a-1)*n + b;
        int y = (c-1)*n + d;
        vec[x].pb(y);
    }
    bfs(1);
    cout << ans << endl;
#ifdef DEBUG
    //freopen(D:\in.txt,r,stdin);
#endif
    return 0;
}